SDN World 3 Ship Design Thread

[Steve]

1921 for earliest use. That's when I put it on my own Large Cruiser.

[Norseman]

1921 for earliest use. That's when I put it on my own Large Cruiser.

Aaaah in that case my design project becomes much easier...

[Sea Skimmer]

Steve I have a ship of far less tonnage and better lines, mine have 160 000 hp the lexingtons have 180 000. Quite frankly my ships should be a lot faster than the Lexingtons. Indeed I dare you to see how many horsepowers you'll need to get that kind of speed with a Lexington build in Springsharp. Indeed to match the Lexingtons speed Springsharp tells me I'd need 200 000 hp and that's just insane.

Why? The real Lexington developed 209,000shp on trial and never did quite hit 35 knots.

[Norseman]

Steve I have a ship of far less tonnage and better lines, mine have 160 000 hp the lexingtons have 180 000. Quite frankly my ships should be a lot faster than the Lexingtons. Indeed I dare you to see how many horsepowers you'll need to get that kind of speed with a Lexington build in Springsharp. Indeed to match the Lexingtons speed Springsharp tells me I'd need 200 000 hp and that's just insane.

Why? The real Lexington developed 209,000shp on trial and never did quite hit 35 knots.

Hrm... I guess the issue is really how accurately Springsharp represents engine weights and the power requirements to reach certain speeds.

[Sea Skimmer]

It doesn’t give you the ability to have a highly optimized hull form, but for large ships the values are not unrealistic. Also Springsharp has no weight penalty at all for turboelectric drives, which is a huge savings on a Lexington. The Lexington’s also drew much less water then your design does while having somewhat more beam. Your ships displacement falls right in-between the size of the 1916 Lexington BC which was designed for 35 knots and the revised 1919 design which was designed for 33.25 knots. The carrier conversion was closer in weight to the 1916 design and thus was able to reach 34 knots, but with a power plant which output well over the design figure. Meaning the design speeds for the battlecruiser versions would not have been met on trial.

So all and all I see no inaccuracy at work here at all. The lack of horsepower on your ship is more then in line with its slightly lesser speed. 20,000shp is not a small difference when you could power a 35,000 ton ship to 21 knots on just 40,000shp in total. But of course the true difference is 160 vs 209 to met the spec speed. So that goes back to the fact that in this instance for a Lexington Spring sharp would actually underestimate the machinery weight.

[Lascaris]

And our latest monster

Plan 1925, Cisplatina Enter ship type laid down 1925 (Engine 1926)

Displacement:
52.073 t light; 54.945 t standard; 58.207 t normal; 60.816 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(780,00 ft / 780,00 ft) x 112,00 ft x (40,00 / 41,39 ft)
(237,74 m / 237,74 m) x 34,14 m x (12,19 / 12,62 m)

Armament:
12 - 17,72" / 450 mm 47,0 cal guns - 2.900,01lbs / 1.315,42kg shells, 82 per gun
Breech loading guns in turret on barbette mounts, 1925 Model
3 x 4-gun mounts on centreline ends, majority forward
1 raised mount - superfiring
20 - 5,00" / 127 mm 40,0 cal guns - 59,90lbs / 27,17kg shells, 150 per gun
Dual purpose guns in deck and hoist mounts, 1925 Model
10 x Single mounts on sides, evenly spread
32 - 1,57" / 40,0 mm 60,0 cal guns - 2,14lbs / 0,97kg shells, 600 per gun
Anti-air guns in deck mounts, 1925 Model
8 x Quad mounts on sides, evenly spread
Weight of broadside 36.066 lbs / 16.359 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 15,0" / 381 mm 467,00 ft / 142,34 m 16,50 ft / 5,03 m
Ends: Unarmoured
Main Belt covers 92% of normal length
Main Belt inclined 21,00 degrees (positive = in)

- Torpedo Bulkhead - Additional damage containing bulkheads:
4,00" / 102 mm 467,00 ft / 142,34 m 37,42 ft / 11,41 m
Beam between torpedo bulkheads 92,00 ft / 28,04 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 18,0" / 457 mm 9,00" / 229 mm 15,0" / 381 mm
2nd: 3,00" / 76 mm - -
3rd: 0,50" / 13 mm - -

- Armoured deck - multiple decks:
For and Aft decks: 8,00" / 203 mm

- Conning towers: Forward 5,00" / 127 mm, Aft 2,00" / 51 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 123.801 shp / 92.356 Kw = 28,00 kts
Range 7.400nm at 15,00 kts
Bunker at max displacement = 5.871 tons

Complement:
1.873 - 2.435

Cost:
£19,185 million / $76,739 million

Distribution of weights at normal displacement:
Armament: 7.181 tons, 12,3%
- Guns: 7.181 tons, 12,3%
Armour: 20.687 tons, 35,5%
- Belts: 5.093 tons, 8,7%
- Torpedo bulkhead: 2.586 tons, 4,4%
- Armament: 4.834 tons, 8,3%
- Armour Deck: 7.947 tons, 13,7%
- Conning Towers: 227 tons, 0,4%
Machinery: 3.963 tons, 6,8%
Hull, fittings & equipment: 20.242 tons, 34,8%
Fuel, ammunition & stores: 6.134 tons, 10,5%
Miscellaneous weights: 0 tons, 0,0%

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
65.482 lbs / 29.702 Kg = 23,6 x 17,7 " / 450 mm shells or 10,6 torpedoes
Stability (Unstable if below 1.00): 1,06
Metacentric height 6,7 ft / 2,0 m
Roll period: 18,2 seconds
Steadiness - As gun platform (Average = 50 %): 51 %
- Recoil effect (Restricted arc if above 1.00): 0,93
Seaboat quality (Average = 1.00): 1,03

Hull form characteristics:
Hull has a flush deck,
a normal bow and large transom stern
Block coefficient (normal/deep): 0,583 / 0,589
Length to Beam Ratio: 6,96 : 1
'Natural speed' for length: 32,53 kts
Power going to wave formation at top speed: 51 %
Trim (Max stability = 0, Max steadiness = 100): 49
Bow angle (Positive = bow angles forward): 0,00 degrees
Stern overhang: 0,00 ft / 0,00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20,00%, 30,12 ft / 9,18 m, 24,65 ft / 7,51 m
- Forward deck: 30,00%, 24,65 ft / 7,51 m, 19,17 ft / 5,84 m
- Aft deck: 35,00%, 19,17 ft / 5,84 m, 19,17 ft / 5,84 m
- Quarter deck: 15,00%, 19,17 ft / 5,84 m, 19,17 ft / 5,84 m
- Average freeboard: 21,53 ft / 6,56 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 91,9%
- Above water (accommodation/working, high = better): 136,2%
Waterplane Area: 65.516 Square feet or 6.087 Square metres
Displacement factor (Displacement / loading): 94%
Structure weight / hull surface area: 257 lbs/sq ft or 1.254 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0,95
- Longitudinal: 1,54
- Overall: 1,00
Adequate machinery, storage, compartmentation space
Excellent accommodation and workspace room

[Fingolfin_Noldor]

Well, you certainly sacrificed lots of armor to allow the ship to go at 28knots... my tentative 28kt 18"/45 ship goes around 67Ktonnes and above with armor comparable and better than my current Justinian class.

[CmdrWilkens]

Well, you certainly sacrificed lots of armor to allow the ship to go at 28knots... my tentative 28kt 18"/45 ship goes around 67Ktonnes and above with armor comparable and better than my current Justinian class.

I'd concur, your side belt would be susceptible to any 16"/45 AP rounds and largely susceptible to heavy AP rounds from a 15"/45 or 15"/50 or even some 14"/45s (I'm actually thinking of the 380 mm/45 guns on my 1916 and 1918 series ships). Moreover the same armor only goes 16.5' vertically which leaves a pretty big empty zone on your freeboard. At the same time your side and roof armor on the turrets is really low and your conning tower is just begging to be shot away by secondary guns.

I know my 18"/45 ship only has 10 guns but she shoots better and is massively better armored with the same speed rating and a greater endurance. Now that is for about 5kt of extra displacement but right now this ship is very under armored for its role, unless you are trying for a battlecruiser

[Fingolfin_Noldor]

A ballpark range for armor for such a ship is provided by the Yamato, which has something like a 16" main belt, and up to 9" deck armor. I vaguely recall that my 28kt 18"/45 ship has close to 10" deck if I recall, with 16" main belt 21ft high.

16.5ft is simply too short, really. But then, an extra 2-3 ft would probably substantially increase the weight of the ship. Also, the more barbette armor, the merrier, really.

[Ma Deuce]

Moreover the same armor only goes 16.5' vertically which leaves a pretty big empty zone on your freeboard.

16.5 feet should be sufficient for that design. He only has 19 feet of freeboard amidships, so accounting for the belt's incline (which reduces it's effective height to 15 feet) and assuming it goes 6 feet underwater, that leaves 9 feet above the freeboard, which leaves only one unporotected deck above the belt and main armored deck for most of the citadel. A lot of AoN designs (including the Yamato) had a full two unprotected decks above the belt (then again, they usually had more freeboard as well).

I'd concur, your side belt would be susceptible to any 16"/45 AP rounds and largely susceptible to heavy AP rounds from a 15"/45 or 15"/50 or even some 14"/45s (I'm actually thinking of the 380 mm/45 guns on my 1916 and 1918 series ships)

You're kidding right? Don't forget that his belt is also angled inward 21 degrees, so by your logic Yamato's belt was inadequate against her own guns. Even a 15 inch vertical belt should be immune to 16"/45 gunfire outside 23k yards or so. His inclined belt should be immune to his ship's own 17.7" guns at 20-21k yards.

[Fingolfin_Noldor]

This is one iteration of my own 18"/45 gun ship.

John II Komnenos, Byzantine Empire Battleship laid down 1926

Displacement:
51,327 t light; 55,047 t standard; 58,147 t normal; 60,627 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(855.56 ft / 836.61 ft) x 108.27 ft (Bulges 114.83 ft) x (36.09 / 37.42 ft)
(260.77 m / 255.00 m) x 33.00 m (Bulges 35.00 m) x (11.00 / 11.40 m)

Armament:
9 - 18.00" / 457 mm 45.0 cal guns - 3,000.01lbs / 1,360.78kg shells, 100 per gun
Breech loading guns in turret on barbette mounts, 1926 Model
3 x 3-gun mounts on centreline ends, majority forward
1 raised mount - superfiring
16 - 5.00" / 127 mm 38.0 cal guns - 59.33lbs / 26.91kg shells, 1,800 per gun
Dual purpose guns in deck and hoist mounts, 1926 Model
8 x 2-gun mounts on sides, evenly spread
4 raised mounts
40 - 1.57" / 40.0 mm 56.0 cal guns - 2.12lbs / 0.96kg shells, 2,000 per gun
Anti-air guns in deck mounts, 1926 Model
8 x Twin mounts on side ends, evenly spread
4 raised mounts - superfiring
40 - 0.79" / 20.0 mm 70.0 cal guns - 0.27lbs / 0.12kg shells, 2,000 per gun
Anti-air guns in deck mounts, 1926 Model
8 x Quad mounts on side ends, evenly spread
32 - 0.50" / 12.7 mm 12.0 cal guns - 0.04lbs / 0.02kg shells, 2,000 per gun
Machine guns in deck mounts, 1926 Model
32 x Single mounts on sides, evenly spread
Weight of broadside 28,046 lbs / 12,722 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 16.0" / 406 mm 460.00 ft / 140.21 m 20.00 ft / 6.10 m
Ends: Unarmoured
Main Belt covers 85 % of normal length
Main Belt inclined 20.00 degrees (positive = in)

- Torpedo Bulkhead - Additional damage containing bulkheads:
4.00" / 102 mm 460.00 ft / 140.21 m 33.00 ft / 10.06 m
Beam between torpedo bulkheads 72.00 ft / 21.95 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 22.0" / 559 mm 16.0" / 406 mm 18.0" / 457 mm
2nd: 2.50" / 64 mm 2.50" / 64 mm 2.50" / 64 mm
3rd: 0.50" / 13 mm 0.50" / 13 mm -
4th: 0.50" / 13 mm - -
5th: 0.50" / 13 mm - -

- Armoured deck - multiple decks:
For and Aft decks: 8.10" / 206 mm
Forecastle: 2.00" / 51 mm Quarter deck: 2.00" / 51 mm

- Conning towers: Forward 16.00" / 406 mm, Aft 3.00" / 76 mm

Machinery:
Oil fired boilers, steam turbines,
Electric motors, 4 shafts, 78,005 shp / 58,192 Kw = 24.00 kts
Range 9,000nm at 14.00 kts
Bunker at max displacement = 5,580 tons

Complement:
1,871 - 2,433

Cost:
£16.227 million / $64.907 million

Distribution of weights at normal displacement:
Armament: 5,226 tons, 9.0 %
- Guns: 5,226 tons, 9.0 %
Armour: 23,488 tons, 40.4 %
- Belts: 6,474 tons, 11.1 %
- Torpedo bulkhead: 2,247 tons, 3.9 %
- Armament: 5,654 tons, 9.7 %
- Armour Deck: 8,500 tons, 14.6 %
- Conning Towers: 614 tons, 1.1 %
Machinery: 2,497 tons, 4.3 %
Hull, fittings & equipment: 20,021 tons, 34.4 %
Fuel, ammunition & stores: 6,820 tons, 11.7 %
Miscellaneous weights: 95 tons, 0.2 %
- Hull above water: 20 tons
- On freeboard deck: 75 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
85,521 lbs / 38,792 Kg = 29.3 x 18.0 " / 457 mm shells or 17.0 torpedoes
Stability (Unstable if below 1.00): 1.03
Metacentric height 5.9 ft / 1.8 m
Roll period: 19.8 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.79
Seaboat quality (Average = 1.00): 1.21

Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and a round stern
Block coefficient (normal/deep): 0.587 / 0.590
Length to Beam Ratio: 7.29 : 1
'Natural speed' for length: 28.92 kts
Power going to wave formation at top speed: 40 %
Trim (Max stability = 0, Max steadiness = 100): 58
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 32.81 ft / 10.00 m, 19.69 ft / 6.00 m
- Forward deck: 30.00 %, 19.69 ft / 6.00 m, 19.69 ft / 6.00 m
- Aft deck: 35.00 %, 19.69 ft / 6.00 m, 19.69 ft / 6.00 m
- Quarter deck: 15.00 %, 19.69 ft / 6.00 m, 19.69 ft / 6.00 m
- Average freeboard: 20.73 ft / 6.32 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 84.4 %
- Above water (accommodation/working, high = better): 131.2 %
Waterplane Area: 65,446 Square feet or 6,080 Square metres
Displacement factor (Displacement / loading): 110 %
Structure weight / hull surface area: 239 lbs/sq ft or 1,169 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.99
- Longitudinal: 1.12
- Overall: 1.00
Adequate machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

[Lascaris]

Well, you certainly sacrificed lots of armor to allow the ship to go at 28knots... my tentative 28kt 18"/45 ship goes around 67Ktonnes and above with armor comparable and better than my current Justinian class.

I'd concur, your side belt would be susceptible to any 16"/45 AP rounds and largely susceptible to heavy AP rounds from a 15"/45 or 15"/50 or even some 14"/45s (I'm actually thinking of the 380 mm/45 guns on my 1916 and 1918 series ships). Moreover the same armor only goes 16.5' vertically which leaves a pretty big empty zone on your freeboard. At the same time your side and roof armor on the turrets is really low and your conning tower is just begging to be shot away by secondary guns.

I know my 18"/45 ship only has 10 guns but she shoots better and is massively better armored with the same speed rating and a greater endurance. Now that is for about 5kt of extra displacement but right now this ship is very under armored for its role, unless you are trying for a battlecruiser

Ok, Ma Deuce already covered it but still...

a. The side belt is 15 inches inclined at 21 degrees. That is equal in thickness to the planned N3 class battleships, has three inches on the Iowa, one inch on the G3 and to keep it short only Yamato had a thicker belt. This in my book hardly counts as underarmored. Further as Sea Skimmer has argued before it it physically impossible to make proper armor plate thicker than 14-15 inches in this day and era. Now add to the picture that the belt IS inclined at 21 degrees...

b. Vis a vis the highness the 16.5 feet height is to be blunt a concession to Steve. I'm rather unconvinced it is correct practice to increase the depth of the belt beyond what Springsharp gives you for all or nothing ships. Why? Leaving aside the problematic situation of a ship with icremental armor actually saving weight. Now claiming that noo after all 15-18 feet is not enough lets make it 20 makes it just absurd.

But nevertheless to get to practicalities. Nelson's belts extended from 6.5 feet above the waterline to 5.75 feet below. King George V and the Lions both having exceptionally deep belts extended 10 and 11 feet above the waterline respectively. My design with 16.5 feet extends 10.5 feet above the waterline (or 9.4 if you want to claim that the inclination counts against the height of the belt) Coupled with the somewhat low freeboard it is more than adequate.

c. Deck armor...is 8in. Slightly more than Yamato's 7.87. Enough said.

[Fingolfin_Noldor]

Actually, Yamato's deck is 8-9" if Wiki is to be believed, and inclining your belt means it's actually shorter in reality. In short, your belt is actually 15.5ft high. Trigonmetry really.

[Sea Skimmer]

Yamato had three thicknesses of main deck armor. The vast majority of the deck is 200mm, the deck edge slopes are 230mm to compensate for the fact that they are angled towards a shell impact. This allowed slightly lower belt armor and a small net weight savings. Finally the deck armor over the funnel uptakes was 380mm thick, but extensively drilled with holes. All of this deck armor is meant to offer the same standard of protection, which was to resist the ships own 18in gunfire at 30,000 meters and a 1000kg AP bomb dropped from 3,400 meters.

Yamato also had a 9mm spall shield attached to the underside of the girders holding up the main armor deck. It really couldn’t have stopped more then rivet heads, as heavy spall from deck armor can come in 40lb chunks. Additionally some patches of 50mm thick armor extended fore and aft of the main deck armor to protect against the ships ends from being easily broken up by HE bombs.

[CmdrWilkens]

So switching things up, here is an early cut on my possible 1926-series Destroyer:

Rio Grande, Mexico Destroyer laid down 1926

Displacement:
1,563 t light; 1,616 t standard; 1,800 t normal; 1,947 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(343.81 ft / 341.00 ft) x 33.00 ft x (17.00 / 17.76 ft)
(104.79 m / 103.94 m) x 10.06 m x (5.18 / 5.41 m)

Armament:
5 - 5.00" / 127 mm 38.0 cal guns - 59.33lbs / 26.91kg shells, 100 per gun
Quick firing guns in deck and hoist mounts, 1920 Model
1 x Single mount on centreline forward
1 raised mount - superfiring
2 x 2-gun mounts on centreline ends, evenly spread
8 - 0.79" / 20.0 mm 45.0 cal guns - 0.25lbs / 0.11kg shells, 250 per gun
Anti-air guns in deck mounts, 1920 Model
4 x Twin mounts on sides, evenly spread
4 - 0.50" / 12.7 mm 12.0 cal guns - 0.05lbs / 0.02kg shells, 1,000 per gun
Machine guns in deck mounts, 1909 Model
4 x Single mounts on sides, evenly spread
Weight of broadside 299 lbs / 136 kg
Main Torpedoes
8 - 21.0" / 533 mm, 8.00 ft / 2.44 m torpedoes - 0.617 t each, 4.937 t total
submerged bow & stern tubes
2nd Torpedoes
36 - 21.0" / 533 mm, 8.00 ft / 2.44 m torpedoes - 0.617 t each, 22.217 t total
below water reloads
Main DC/AS Mortars
2 - 450.00 lbs / 204.12 kg Depth Charges + 40 reloads - 8.438 t total
in Stern depth charge racks

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2.00" / 51 mm - 1.00" / 25 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 3 shafts, 46,412 shp / 34,623 Kw = 36.00 kts
Range 5,500nm at 12.00 kts
Bunker at max displacement = 332 tons

Complement:
137 - 179

Cost:
£0.768 million / $3.071 million

Distribution of weights at normal displacement:
Armament: 116 tons, 6.5 %
- Guns: 68 tons, 3.8 %
- Weapons: 48 tons, 2.7 %
Armour: 17 tons, 1.0 %
- Armament: 17 tons, 1.0 %
Machinery: 1,024 tons, 56.9 %
Hull, fittings & equipment: 405 tons, 22.5 %
Fuel, ammunition & stores: 237 tons, 13.2 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
236 lbs / 107 Kg = 3.8 x 5.0 " / 127 mm shells or 0.4 torpedoes
Stability (Unstable if below 1.00): 1.26
Metacentric height 1.4 ft / 0.4 m
Roll period: 11.6 seconds
Steadiness - As gun platform (Average = 50 %): 50 %
- Recoil effect (Restricted arc if above 1.00): 0.42
Seaboat quality (Average = 1.00): 0.70

Hull form characteristics:
Hull has rise forward of midbreak,
a normal bow and large transom stern
Block coefficient (normal/deep): 0.329 / 0.341
Length to Beam Ratio: 10.33 : 1
'Natural speed' for length: 21.57 kts
Power going to wave formation at top speed: 67 %
Trim (Max stability = 0, Max steadiness = 100): 72
Bow angle (Positive = bow angles forward): 8.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 20.00 ft / 6.10 m, 16.00 ft / 4.88 m
- Forward deck: 20.00 %, 16.00 ft / 4.88 m, 16.00 ft / 4.88 m
- Aft deck: 45.00 %, 9.00 ft / 2.74 m, 9.00 ft / 2.74 m
- Quarter deck: 15.00 %, 9.00 ft / 2.74 m, 9.00 ft / 2.74 m
- Average freeboard: 12.12 ft / 3.69 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 218.8 %
- Above water (accommodation/working, high = better): 107.3 %
Waterplane Area: 6,920 Square feet or 643 Square metres
Displacement factor (Displacement / loading): 56 %
Structure weight / hull surface area: 34 lbs/sq ft or 164 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.45
- Longitudinal: 1.46
- Overall: 0.50
Extremely poor machinery, storage, compartmentation space
Adequate accommodation and workspace room
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

This last line is the kicker, I can't seem to design a DD without having poor seakeeping as a trait. Any advice for this because I've turned the trim way up and still can't seem to get better than .7 or .71?

[Steve]

Honestly it's a limitation on SpringSharp, your ship's not long enough to have a natural speed anywhere close to 35+ knots. So your seakeeping is brutally capped.

[Norade]

That's odd, most of my designs end up at 2.00 sea keeping and 0.5 or 0.51 hull strength. I couldn't say why though.

At slight odds with Steve's experience my design has 34 knots maximum speed.

Class-3, Portugal Destroyer laid down 1919

Displacement:
2,036 t light; 2,127 t standard; 2,331 t normal; 2,494 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(492.13 ft / 492.13 ft) x 36.09 ft x (13.12 / 13.66 ft)
(150.00 m / 150.00 m) x 11.00 m x (4.00 / 4.16 m)

Armament:
6 - 4.72" / 120 mm 45.0 cal guns - 53.17lbs / 24.12kg shells, 150 per gun
Quick firing guns in deck mounts, 1919 Model
3 x Twin mounts on centreline, forward deck aft
2 - 0.50" / 12.7 mm 45.0 cal guns - 0.06lbs / 0.03kg shells, 300 per gun
Quick firing guns in deck mounts, 1919 Model
2 x Single mounts on sides, forward deck aft
Weight of broadside 319 lbs / 145 kg
6 - 24.0" / 610 mm, 25.00 ft / 7.62 m torpedoes - 2.047 t each, 12.283 t total
In 2 sets of submerged side tubes
3 - 24.0" / 610 mm, 25.00 ft / 7.62 m torpedoes - 2.047 t each, 6.142 t total
In 2 sets of submerged bow tubes

Machinery:
Diesel Internal combustion motors,
Geared drive, 2 shafts, 42,147 shp / 31,442 Kw = 34.00 kts
Range 5,000nm at 12.00 kts
Bunker at max displacement = 366 tons

Complement:
167 - 218

Cost:
£0.576 million / $2.304 million

Distribution of weights at normal displacement:
Armament: 65 tons, 2.8 %
- Guns: 46 tons, 2.0 %
- Torpedoes: 18 tons, 0.8 %
Machinery: 1,267 tons, 54.4 %
Hull, fittings & equipment: 659 tons, 28.3 %
Fuel, ammunition & stores: 295 tons, 12.7 %
Miscellaneous weights: 44 tons, 1.9 %
- Hull below water: 36 tons
- On freeboard deck: 8 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
372 lbs / 169 Kg = 7.1 x 4.7 " / 120 mm shells or 0.2 torpedoes
Stability (Unstable if below 1.00): 1.21
Metacentric height 1.5 ft / 0.5 m
Roll period: 12.3 seconds
Steadiness - As gun platform (Average = 50 %): 100 %
- Recoil effect (Restricted arc if above 1.00): 0.33
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.350 / 0.360
Length to Beam Ratio: 13.64 : 1
'Natural speed' for length: 22.18 kts
Power going to wave formation at top speed: 52 %
Trim (Max stability = 0, Max steadiness = 100): 67
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 26.25 ft / 8.00 m, 16.40 ft / 5.00 m
- Forward deck: 30.00 %, 16.40 ft / 5.00 m, 16.40 ft / 5.00 m
- Aft deck: 35.00 %, 16.40 ft / 5.00 m, 16.40 ft / 5.00 m
- Quarter deck: 15.00 %, 16.40 ft / 5.00 m, 9.84 ft / 3.00 m
- Average freeboard: 16.70 ft / 5.09 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 232.3 %
- Above water (accommodation/working, high = better): 198.4 %
Waterplane Area: 10,604 Square feet or 985 Square metres
Displacement factor (Displacement / loading): 73 %
Structure weight / hull surface area: 30 lbs/sq ft or 149 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.45
- Longitudinal: 1.35
- Overall: 0.50
Hull space for machinery, storage, compartmentation is extremely poor
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

I have not a shred of armor, but I don't see how that would effect anything like sea keeping or stability in any unusual way.

[CmdrWilkens]

That's odd, most of my designs end up at 2.00 sea keeping and 0.5 or 0.51 hull strength. I couldn't say why though.

At slight odds with Steve's experience my design has 34 knots maximum speed.

I have not a shred of armor, but I don't see how that would effect anything like sea keeping or stability in any unusual way.

Part of it is the ridiculous length to beam ratio for a destroyer....seriously 492' long? The thing is like a needle boat with guns.

[Steve]

Yeah, that's what's doing it, plus SpringSharp doesn't allow for the kind of hull-shaping that would let a destroyer be better at seakeeping than it claims at shorter lengths.

[Norade]

Yeah, I do suppose that she is a needle with guns, but a fast stable needle with guns is she. Though I wouldn't want to get into too many turning fights...

[CmdrWilkens]

Yeah, that's what's doing it, plus SpringSharp doesn't allow for the kind of hull-shaping that would let a destroyer be better at seakeeping than it claims at shorter lengths.

It makes me want to just add about 100' of length to represent the advantages of proper hull form so that a 450' ship is "really" 350'. Anyway I'm going to experiment with my design adding some length and otherwise tweaking the freeboard to see if i can get better seakeeping.

[Lascaris]

Actually, Yamato's deck is 8-9" if Wiki is to be believed, and inclining your belt means it's actually shorter in reality. In short, your belt is actually 15.5ft high. Trigonmetry really.

15.4 feet if we want to be exact. IF springsharp bothers with such minutiae.

Still means 9.65 feet above the waterline or 50% more than Nelson and only 10 cm less than King George V. Given that Nelson the sole modern 1920s design...

[Ryan Thunder]

Vendetta, Gran Colombia Battleship laid down 1925

Displacement:
46 840 t light; 49 123 t standard; 55 000 t normal; 59 702 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(869.42 ft / 869.42 ft) x 98.43 ft x (28.54 / 30.75 ft)
(265.00 m / 265.00 m) x 30.00 m x (8.70 / 9.37 m)

Armament:
6 - 17.72" / 450 mm 50.0 cal guns - 2 976.24lbs / 1 350.00kg shells, 100 per gun
Breech loading guns in turret on barbette mounts, 1925 Model
3 x Twin mounts on centreline ends, majority forward
1 raised mount - superfiring
16 - 5.91" / 150 mm 50.0 cal guns - 110.23lbs / 50.00kg shells, 150 per gun
Quick firing guns in turret on barbette mounts, 1925 Model
8 x Single mounts on side ends, evenly spread
4 raised mounts - superfiring
18 - 3.15" / 80.0 mm 60.0 cal guns - 17.64lbs / 8.00kg shells, 200 per gun
Anti-air guns in deck mounts, 1925 Model
18 x Single mounts on sides, aft evenly spread
72 - 0.57" / 14.5 mm 60.0 cal guns - 0.10lbs / 0.05kg shells, 2 000 per gun
Machine guns in deck mounts, 1925 Model
18 x Quad mounts on sides, evenly spread
Weight of broadside 19 946 lbs / 9 047 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 17.7" / 450 mm 639.76 ft / 195.00 m 19.69 ft / 6.00 m
Ends: Unarmoured
Main Belt covers 113 % of normal length
Main Belt inclined -20.00 degrees (positive = in)

- Torpedo Bulkhead - Strengthened structural bulkheads:
1.97" / 50 mm 639.76 ft / 195.00 m 32.81 ft / 10.00 m
Beam between torpedo bulkheads 98.43 ft / 30.00 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 15.7" / 400 mm 7.87" / 200 mm 15.7" / 400 mm
2nd: 0.98" / 25 mm 0.98" / 25 mm 0.98" / 25 mm

- Armoured deck - multiple decks:
For and Aft decks: 7.87" / 200 mm

- Conning towers: Forward 7.87" / 200 mm, Aft 7.87" / 200 mm

Machinery:
Diesel Internal combustion generators plus batteries,
Electric motors, 4 shafts, 91 995 shp / 68 628 Kw = 25.00 kts
Range 15 000nm at 15.00 kts
Bunker at max displacement = 10 579 tons

Complement:
1 795 - 2 334

Cost:
£13.391 million / $53.564 million

Distribution of weights at normal displacement:
Armament: 3 692 tons, 6.7 %
- Guns: 3 692 tons, 6.7 %
Armour: 23 504 tons, 42.7 %
- Belts: 9 323 tons, 17.0 %
- Torpedo bulkhead: 1 529 tons, 2.8 %
- Armament: 3 800 tons, 6.9 %
- Armour Deck: 8 361 tons, 15.2 %
- Conning Towers: 491 tons, 0.9 %
Machinery: 2 987 tons, 5.4 %
Hull, fittings & equipment: 16 582 tons, 30.1 %
Fuel, ammunition & stores: 8 160 tons, 14.8 %
Miscellaneous weights: 75 tons, 0.1 %
- On freeboard deck: 75 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
109 504 lbs / 49 670 Kg = 39.4 x 17.7 " / 450 mm shells or 18.5 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 6.2 ft / 1.9 m
Roll period: 16.6 seconds
Steadiness - As gun platform (Average = 50 %): 71 %
- Recoil effect (Restricted arc if above 1.00): 0.95
Seaboat quality (Average = 1.00): 1.54

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.788 / 0.794
Length to Beam Ratio: 8.83 : 1
'Natural speed' for length: 29.49 kts
Power going to wave formation at top speed: 42 %
Trim (Max stability = 0, Max steadiness = 100): 46
Bow angle (Positive = bow angles forward): 0.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 36.09 ft / 11.00 m, 29.53 ft / 9.00 m
- Forward deck: 20.00 %, 29.53 ft / 9.00 m, 22.97 ft / 7.00 m
- Aft deck: 40.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m
- Quarter deck: 20.00 %, 22.97 ft / 7.00 m, 22.97 ft / 7.00 m
- Average freeboard: 25.46 ft / 7.76 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 51.7 %
- Above water (accommodation/working, high = better): 190.0 %
Waterplane Area: 74 407 Square feet or 6 913 Square metres
Displacement factor (Displacement / loading): 112 %
Structure weight / hull surface area: 190 lbs/sq ft or 928 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 1.00
- Longitudinal: 1.01
- Overall: 1.00
Excellent machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[Steve]

I presume you mean laid down in 1921-22 if you want it in service?

[Ryan Thunder]

I presume you mean laid down in 1921-22 if you want it in service?

It's not in service. This is a new design. I already made up my naval ORBAT, remember?

There may be some things I've forgotten to add to it (lolcoastal fortresses), but this isn't one of those things.